Brainstem DisordersDan Gold, DO

Assistant Professor of Neurology, Ophthalmology, Neurosurgery, Otolaryngology – Head & Neck Surgery

The Johns Hopkins University School of Medicine

Relevant Financial

Disclosures

• I have no financial interests or relationships to

disclose.

Outline• 1) Lateral Medullary Syndrome

• Saccadic dysmetria

• Nystagmus

• Semicircular canal & utricle imbalance

• 2) Medial Longitudinal Fasciculus Syndrome

• Nystagmus

• Semicircular canal & utricle imbalance

• 3) Oculopalatal Tremor

1) Lateral Medullary

(Wallenberg)

Syndrome

Lateral Medullary

SyndromeSACCADIC DYSMETRIA & OCULAR

LATEROPULSION

Is the lateral medullary lesion on

the right or the left?

RIGHT

Is the lateral medullary lesion on

the right or the left?

LEFT

Left lateral medullary lesion

R L

R L

Disruption of

climbing fibers

(ICP)

Simple spike (inhibitory)

discharge of Purkinje cells

increases

R L

Increased Purkinje firing increased fastigial inhibition

Inhibition of

fastigial nucleus…

R L

…Decreased

excitation of

contra IBN

R L

Decreased inhibition of left VIth N & PPRF results in

overaction of these structures, bias towards the

left

PEARL: End result with L Wallenberg is L

hypermetria & L ocular lateropulsion

R L

Lateral Medullary

SyndromeNYSTAGMUS

Unidirectional Nystagmus

Is this right 8th nerve or right lateral medullary?

Peripheral SCC imbalance

Central SCC imbalance

Semicircular canals (SCC) – angular acceleration detectors

Unopposed L PC

+ L HC + L AC

Result is mixed left-beating mixed

horizontal-torsional nystagmus

PEARL: At the level of the labyrinth/8th N & medulla, nystagmus can be UNIDIRECTIONAL &

indistinguishable

Torsional Nystagmus

Is this right 8th nerve or right lateral medullary?

PEARL: Pure TORSIONAL nystagmus is

almost always central

Can you have pure torsional nystagmus

from a peripheral lesion?

Gaze-Evoked Nystagmus

PEARL: MVN-NPH responsible for horizontal

gaze-holding GAZE-EVOKED NYSTAGMUS

Wernicke’s encephalopathy

Lateral Medullary

SyndromeVESTIBULO-OCULAR REFLEX

Is this vestibular neuritis or lateral medullary?

Abnormal Head Impulse Test (HIT) to the RIGHT

RIGHT Vestibular neuritis

Damage to horizontal SCC fibers in 8th nerve

Is this vestibular neuritis or lateral medullary?

Abnormal Head Impulse Test (HIT) to the LEFT

LEFT Wallenberg

Damage to horizontal SCC fibers synapsing in the MVN

PEARL: While an abnormal (+) HIT

is almost always indicative of a

peripheral etiology, certain central

localizations (vestibular nucleus)

can cause this finding

Lateral Medullary

SyndromeUTRICULAR-OCULAR REFLEX

Utricle – linear acceleration detector, responds to

translation & head tilt

Physiologic Ocular Tilt Reaction (OTR)

1) Head tilts right

2) Right eye elevates &

Left eye depresses

3) Ocular counter-roll

towards left ear

Skew Deviation

Pathologic OTR from Wallenberg on LEFT(PEARL: caudal to decussation of utricle-ocular motor fibers, ipsi-

hypotropia)

PEARL: Although a “peripheral” skew is possible, it is rare and usually

small. Presence of a skew should be

considered central until proven otherwise.

2) Medial Longitudinal

Fasciculus (MLF)

Syndrome

Left INO due to left MLF injury

What we won’t talk about

MLF SyndromeNYSTAGMUS

MLF lesions – PEARL: Torsional nystagmus is ipsiversive &vertical components can be dissociated

Why?

Most common patterns• Ipsiversive torsional component &…

• 1) UBN OU, more in the contralateral eye

• 2) DBN OU, more in the ipsilateral eye

• 3) Jerky (or hemi-) seesaw nystagmus with dissociated vertical components

• UBN in the contralateral eye

• DBN in the ipsilateral eye

How can the ipsiversive torsional

nystagmus be explained?

Semicircular Canal Pathways

Slow (contraversive) torsional phase towards right ear & Fast (ipsiversive) torsional phase toward left ear

PEARL: Left MLF injury damages PC & AC pathways originating in Right Labyrinth

R L R L

PEARL: Ipsiversive torsional nystagmus can be generated by

vertical (posterior & anterior) SCC asymmetry

Skew deviation with Left hypertropia(PEARL: rostral to decussation of utricle-ocular motor fibers,

ipsi-hypertropia)

What produces dissociated

vertical components?

1) Semicircular Canal Pathways

Stimulate R PC (BPPV) activate R SO, L IR

Slow phase down/towards left earFast phase up/towards right ear

Torsional towards left ear; more DB OS

Weaker L IR

Stronger L SR upward slow phase more DB OS (ipsilesional to MLF)

Torsional towards left ear; more UB OD

Weaker R SR

Stronger R IR downward slow phase more UB OD (contralesional to MLF)

What produces dissociated

vertical components?

2) Utricle-ocular motor

Pathways

Left MLF lesion causes Left hypertropia &

Right hypotropia

Skew (OS) – slow phase

up; fast phase down

Skew (OD) – slow phase

down; fast phase up

PEARL: Fast phases UB OD, DB OS

“Jerky see-saw”

MLF SyndromeVESTIBULO-OCULAR REFLEX

3 pathways for

anterior SCC

1 pathway for

posterior SCC

PEARL: PC VOR more affected

than AC VOR with MLF lesions

May experience oscillopsia from

vertical SCC weakness

PEARL:Abnormal HIT (VOR) in the planes of the posterior

canalsNormal HIT (VOR) in the planes of the anterior canals

MS patient with bilateral MLF lesions

3) Oculopalatal

Tremor (OPT)

Central tegmental tract

Guillain-Mollaret’s triangle

CTT normally inhibits IO

CTT injury IO hypertrophy & spontaneous discharges

Take Home Points• 1) Lateral Medullary Syndrome

• Ipsilesional hypermetria and ocular lateropulsion

• Ipsilesional hypotropia

• Can have an abnormal VOR

• Can have unidirectional nystagmus

indistinguishable from “peripheral” nystagmus

• Or, gaze-evoked nystagmus, torsional nystagmus

Take Home Points• 2) MLF Syndrome

• Ipsilesional hypertropia

• Dissociated torsional (ipsiversive)-vertical

nystagmus

• Most common is more UB in contralesional eye

• VOR abnormality in the planes of the posterior

canals

Take Home Points

• 3) OPT

• Guillain Mollaret’s triangle

• Commonly seen with horizontal gaze palsies,

related to central tegmental tract pathology

• Don’t forget to look at the palate when pendular

nystagmus is present!